Method and apparatus for introducing sealing elements into well casings



HIGH PRESSURE PUMPS J. BUCY El AL PPARATUS FOR INTRODUCING AND A NG ELEMENTS INTO WELL CASINGS Filed June 26, 1957 METHOD SEALI April 25, 1961 TO WELL HEAD alll t h f METHOD AND APPARATUS FQR GDUCING SEALING ELEMENTS INTO WELL CASWGS Billy J. Bncy and Charles M. Simmons, Midland, Tex assignors to The Western Company of North America, a corporation of Delaware Filed June 26, 1957, Ser. No. 668,157

4 Claims. (Cl. 166-75) This invention relates to devices for feeding or injecting objects into a vessel under pressure and more particularly to an injection device for introducing sealing elements adapted to temporarily seal perforations in the casing of a well during the treatment of the well with fluid under pressure.

It is common practice to set casing in a well bore hole, to anchor the casing in the well with cement, and then perforate those sections of the casing and surrounding cement sheath set through producing earth formations in order to provide communication between the formations and. the well. Various known means of perforating the casing are employed, as, for example, by explosively propelled bullets and shaped explosive charges.

In completing new oil, gas or water production or injection wells, or in renovating old wells, it is often necessary to open drainage channels or fractures in the earth formations surrounding the casing to allow production of fluid from or injection of fluid into the formations. in such cases it has become common practice to pump fluid down the casing under pressures ranging up to 10,000 p.s.i.g., or more, in order to hydraulically fracture the formations surrounding the perforated sections of the well casing. Oil, water or other fluids employed in hydraulic fracturing operations are usually loaded with sand which serves to prop open the fractures in the formation produced by these treatments. New drainage channels are often opened up in calcareous formations by a treatment with hydrochloric acid, as well as the hydraulic fracturing technique discussed hereinabove.

It is often desired to acidize or hydraulically fracture a single long zone or two or more short zones at different depths in a well. This has previously been difficult and expensive to accomplish since different pressures are normally required to inject fluid into formations at different depths in a well and consequently only that zone or section of a zone which takes fluid under the lowest injection pressure is treated. A new method designed to solve this problem is disclosed in the co-pending application of Charles M. Simmons, Serial No. 615,687, filed October 12, 1956, entitled Method for Temporarily Sealing Perforations in Well Casing. This method consists essentially in introducing well-casing sealing ele ments having a larger diameter than the perforations in the well easing into the well while maintaining the treatment pressure. The well-casing sealing elements thus introduced follow the flow of treating fluid down into the well where they are forced by fluid pressureagainst the perforations in the well casing through which the treating fluid flows at the lowest pressure. Continued pumping of treating fluid into the well having the casing perforations temporarily sealed in this manner causes the internal pressure in the casing to rise sufiiciently to result in a breakdown of the formation opposite perforations which did not receive the treating fluid initially.

2,981,335 Patented Apr. 25, 1961v 2 Thus, it is possible by utilizing the method of said Simmons patent application to treat substantially completely the exposed formations in a well regardless of the fact that the pressure required to inject fluid into different exposed formations or different portions of a single formation may vary over a considerable range.

The method of said Simmons patent application re quires that the fluid pressure in the Well casing be maintained in excess of the back pressure existing in the formation initially receiving fluid since a decrease in the fluid pressure in the well casing below the back pressure might allow well-casing sealing elements already in place in the casing perforations to drop to the bottom of the well. Thus it is necessary to provide means by which both the initial and all succeeding batches of well-casing sealing elements may be injected intothe well while maintaining sufficient hydraulic pressure in the casing to prevent release of well-casing sealing elements from previously sealed perforations. Before treatment of a given well is commenced, the number of perforations in the perforated section of the well casing to be treated is generally known making it possible to estimate the number of well-casing sealing elements required for a successful treatment.

It is a principal object of this invention to provide an injection apparatus and method whereby well-casing sealing elements may be introduced into a cased well during a hydraulic treatment of the well.

It is a further object of this invention to provide means whereby the number of well-casing sealing elements introduced into the well casing may be easily and accurately determined and the time of introduction easily controlled.

It is a still further object of this invention to provide means whereby different techniques of injecting wellcasing sealing elements may be practiced, varying from the injection of well-casing sea-ling elements in one or more batches to the injection of sealing elements uniformly throughout the treatment process.

Further objects and advantages of this invention will be apparent from the following description thereof and the accompanying drawing in which:

Figure 1 is a diagrammatic view, partly in section, of one preferred embodiment of an injector apparatus for introducing well-casing sealing elements into a well treatment line or well casing; and V Figure 2 is an elevational View, partly in section, of an alternative form of a component of a well-casing sealing element injector apparatus designed to prevent premature release of well-casing sealing elements into the well treatment line.

As shown in Figure l, a typical injector apparatus of the present invention comprises a high pressure positive displacement pump 10 connected by a line 11 to one or more injector tubes 12, each of which contains a valve 13. A pressure gauge 14, which per se does not form a part of the invention, may be located, as shown, in line 11 between the pump 10 and the valves 13. Float chamber 15, which is connected to the pump 10 by pipe 16, serves as a reservoir for hydraulic fluid 17 for the pump 10. A free piston 18 is slidably mounted in each of the injector tubes 12 so as to prevent the passage of fluid past said piston toward the injection line, or in either direction. The pistons 18 are capable of movement within the injector tubes between an initial position at the pump end of the injector tubes Where they are located when the tubes are loaded with wellcasing sealing elements, and a terminal position at the dispensing end of the tubes where they are located when all of the well-casing sealing elements have been ejected.

Stops may be provided at each end of the injector tube to prevent the free piston 13 from passing beyond either its initial or terminal positions. Well-casing sealing elements 15 which are shown as rubber balls, are suitably in diameter and made of 70 durometer Hycar rubber, although, as disclosed in the Simmons application referred to above, they may take many other forms, such as ovoid, conoid or polygonal shaped objects. In any event, the well-casing sealing elements must be slightly smaller in diameter than the inside diameter of the injector tubes and slightly larger in diameter than the diameter of the perforations in the well casing. The well-casing sealing elements '19 are loaded into each of the injector tubes 12 ahead of the free piston 18 and retained in said injector tubes by means of spring wire keepers 20 or equivalent means. The injector tubes may be loaded with well-casing sealing elements by disconnecting the injector tubes from the treatment line and inserting the sealing elements at the dispensing end of the injector tubes. The injector tubes may in the alternative be loaded through a port (not shown) near the dis pensing end of the injector tube, which port is closed by a plug after the tube is loaded. If reloading is contemplated during the treatment process, it is then necessary to provide a valve between the dispensing end of the injector tube and the treatment line so that the pressure in the injector tube may be reduced to atmospheric pressure while the pressure in the treatment line is maintained. The necessity for reloading during treatment is generally obviated by the provision of a plurality of injector tubes in the preferred form of the apparatus as shown. .The injector tubes are connected to the treatment line 21 between the high pressure treating fluid pump 22 and the well head (not shown) or, if desired, to the well head, although this is not preferred.

When it is desired to inject the well-casing sealing elements into the well, valve 13 in one or more of the injector tubes 12 is opened, and pump is started. Hydraulic fluid 17 is pumped from the float chamber 15 through pipe line 16 and then line 11 and the resulting hydraulic pressure is communicated to the free piston 18 which forces the sealing elements 19 past the spring wire keepers 2t) and into the stream of treating fluid in the treatment line 21. The amount of hydraulic fluid removed from the float chamber 15 is proportional to that introduced into each injector tube 12 behind the free piston 18. Thus it is possible to calibrate the float gauge 28 mounted in the float chamber 15 to indicate directly the number of well-casing sealing elements injected into the well through the treatment line 21.

, An alternative restraining means which may be used in place of the spring keeper 20 is shown in Figure 2. in this form of restraining means, a lever 23 is piovtally mounted on the inner Wall of the injector tube 12. The lever 23 is normally held away from the wall of the injector tube 12 by a compression spring 24 one end of which acts against the lever 23 while the other end acts against a hollow compression adjustment screw 25, which is mounted in the wall of the injector tube 12. When pressure is applied to the sealing elements 19 by means of fluid pressure acting on the free piston 13, the sealing elements will be forced past the pivotally' mounted lever 23 which will be thereby forced against the wall of the injector tube 12. The difierential pressure required to eject the sealing elements 19 from the injector tube 12 may be varied by turning the compression adjustment screw 25.

It will be appreciated that, although the well-casing sealing elements shown in the drawing are spherical, the invention may be practiced with well-casing sealing elements of a variety of shapes, sizes, densities or materials.

The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions to exclude equivalents of the features shown and described or portions thereof since it is recognized that various modifications are possible within the scope of the invention claimed,

What is claimed is:

1. Apparatus for injecting well-casing perforation sealing elements into a well during the treatment of said well with fluid under pressure, which. comprises at least one injector tube adapted to contain a plurality of wellcasing perforation sealing elements, said injector tube communicating with a well treatment means at one end and with a source of fluid under pressure at the other end, said injector tube being equipped with resilient restraining means adjacent said well-treatment means which restraining means is capable of being displaced when pressure is exerted upon it to permit the escape of said well-casing perforation sealing elements into the welltreatment means, a fluid reservoir means containing hydraulic fluid, said reservoir and fluidbeing independent of the well and well-treatment means, said source of fluid under pressure comprising a pumping means communicating with said reservoir and said injector tube, a free piston means slidably mounted in said injector tube capable of being acted upon by said fluid under pressure and capable of ejecting said well-casing perforation sealing elements through said restraining means.

2. Apparatus for injecting well-casing perforation sealing elements into a well during the treatment of said well with fluid under pressure, which comprises a reservoir adapted to contain hydraulic fluid, a fluid pump connected to said reservoir, at least one elongated injector tube having an inlet and outlet end and adapted to contain well-casing perforation sealing elements, individual valve means associated with the inlet end of said injector tube and providing communication between said fluid pump and said injector tube, free piston means slidably mounted within said injector tube and adapted to be moved progressively by hydraulic pressure from an initial position adjacent to the inlet end of said injector tube to a final position adjacent to the outlet end of said injector tube so as to expel at least one of said sealing elements during such movement, and resilient restraining means located adjacent to the outlet end of said elongated tube for yieldably resisting the passage of sealing elements passed through and out of said injector tube by the hydraulic pressure actuated piston means.

3. Apparatus for injecting well-casing perforation seal ing elements into a well during the treatment of said Well with fluid under pressure, which comprises at least one injector tube, each said injector tube communicating with a well-treatment means at one end and with a source of fluid under pressure at the other end, a plurality of well-casing sealing elements contained in each said injector tube, resilient restraining means within each said injector tube and adjacent said well-treatment means. fluid impermeable free piston means slidably mounted in said injection tube between said sealing elements and said source of fluid under pressure and in direct contact with both said sealing elements and said fluid under pressure such that an application of said fluid under pressure to said piston will eject said sealing elements through said restraining means into said Well-treatment means.

4. Apparatus for injecting well-casing perforation sealing elements into a well during the treatment of said well with fluid under pressure, which comprises at least one injector tube, each said injector tube having an inlet end and an outlet end, each said injector tube communicating with a well-treatment means at its outlet end and with a source of fluid under pressure at its inlet end, a plurality of well-casing sealing elements contained in each said injector tube, individual valve means associated with the inlet end of each said injector tube and providing communication between each said injector tube and said source of fluid under pressureQfluid impermeable free piston meansslidably mounted within said injector tube and adapted to be moved progressively by fiuid under pressure from an initial position adjacent to the inlet end of each said injector tube to a final posi- References Cited in the file of this patent UNITED STATES PATENTS tion adjacent to the outlet end of each said injector tube 1,238,895 Dempsey p 4, So as to expel at least one of said sealing element dur- 5 2,601,852 Wendi July 1, ing such movement, and resilient restraining ns 1 2,642,268 Armentrout June 16,

, cated adjacent to the outlet end of said elongated tube f 2,698,582 cent J an. 4, 1955 yieldably resisting the passage of sealing el ment passed 2,752,067 K0hl et a1. June 26, through and out of said injector tube by the fluid pres- 2,754,910 Demck et y 17, sure actuated piston means. 10 2,790,500 Jones Apr. 30, 

